Polycentric Knee Prosthesis with Dynamic Instantaneous Center of Rotation
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Solution Overview
Problem
Existing lower limb prostheses, particularly those with monocentric mechanisms, face challenges in replicating the natural polycentric movement of the human knee, leading to inefficiencies in weight distribution and stability during various gait phases, especially when navigating slopes or stairs.
Innovation Solution
A polycentric linkage system for the knee prosthesis is introduced, featuring a piston and cylinder assembly with pivot axes that allow the instantaneous center of rotation to change, mimicking the human knee's movement by integrating sensors and adaptive control systems for hydraulic resistance adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a monocentric mechanism with fixed instantaneous centre of rotation is used, then the device complexity is reduced, but the stability and natural movement are compromised
Solution Approach 1:
The patent implements a polycentric mechanism where the instantaneous centre of rotation (ICR) dynamically changes position during the gait cycle. The ICR moves from a posterior position during swing phase to an anterior position during stance phase, allowing the mechanism to adapt to different functional requirements and improve stability while maintaining reasonable complexity
Solution Approach 2:
The mechanism changes the geometric parameters of the knee joint by varying the ICR position according to the gait phase. This parameter change allows optimization of weight distribution and stability characteristics for different phases of movement, resolving the contradiction between simplicity and stability
2Stability of the object's composition
If a polycentric linkage system is implemented, then the stability and natural movement are improved, but the device complexity increases
Solution Approach 1:
The polycentric linkage uses dynamic ICR movement to improve stability on uneven surfaces while managing complexity through controlled motion patterns that replicate natural knee behavior during gait
Solution Approach 2:
The mechanism uses the user's own movement and body weight to drive the polycentric linkage, allowing the system to self-regulate and adapt without requiring complex external control systems, thus improving stability while limiting complexity growth
3Device complexity
If the piston and cylinder assembly is positioned closer to the knee pivot, then the device complexity is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise dimensional parameters for the piston-cylinder assembly positioning, with the distal pivot axis located at a distance of 20-40% of the distance from the anterior knee pivot axis to the foot component. This parameter specification balances assembly integration with manufacturability by providing clear design guidelines
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the stability and natural movement of the prosthesis, improving weight distribution and ease of use on uneven surfaces, while also allowing for a more compact and integrated design with simplified manufacturing.
Implementation Method 1
integrate sensors and adaptive control systems for hydraulic resistance adjustment
Data Source
Figure 1A
Figure 1B
Figure 2~3
AI summary
A lower limb prosthesis comprises a knee chassis (10), a shin carrier (20) pivotally connected to the knee chassis (10) and a piston and cylinder assembly (30, 40) pivotally connected to the knee chassis (10) and the shin carrier (20). The piston and cylinder assembly (30, 40) comprises a piston assembly (40) comprising a piston (44) mounted on a piston rod (42), a cylinder body (32) having a cavity defining a cylinder within which the piston (44) is arranged to reciprocate along the piston and cylinder assembly axis, and a foot component attachment means (36) for attaching a foot component to the piston and cylinder assembly (30, 40).